With the advent of nearly air-tight passenger compartments for automobile bodies, the need has arisen to provide venting which will permit the escape of air pressure occasioned by the slamming or rapid closure of the vehicle door while preventing the entry of outside air. U.S. Pat. Nos. 4,691,623 and 4,972,765 disclose devices for permitting the escape of air from the passenger compartment to the outside of the body. The devices disclosed in these patents require two or more parts to be assembled together, such as a frame structure and a valve structure, and this necessarily raises the cost of the device.
Other patents showing one-way check valves are: U.S. Pat. Nos. 2,249,557; 1,881,929; 3,568,977; 4,324,097.
Of these, U.S. Pat. Nos. 2,249,557 and 1,881,929 show a flap which is formed integrally with the valve seat. In both cases the flap and valve seat are formed of the same material and only gravity serves to bias the flap against the valve seat, and as a consequence the flap may readily flutter open.